Q: 10
You work for a car manufacturer and have set up a data pipeline using Google Cloud Pub/Sub to
capture anomalous sensor events. You are using a push subscription in Cloud Pub/Sub that calls a
custom HTTPS endpoint that you have created to take action of these anomalous events as they
occur. Your custom HTTPS endpoint keeps getting an inordinate amount of duplicate messages. What
is the most likely cause of these duplicate messages?
Options
Discussion
Option B is correct. When your endpoint has an out-of-date SSL certificate, Cloud Pub/Sub can't confirm delivery due to failed TLS handshake, so it keeps retrying and you get duplicate messages. Option D is tempting since missing acks also trigger retries, but this scenario is specific to SSL issues with push endpoints. Seen similar guidance in Google docs. Open to other takes though if anyone's seen differently!
Option B actually makes sense here. If the SSL cert is out-of-date, Pub/Sub’s push will get handshake failures and treat it like a non-ack, which leads to retries and so you get duplicates. I know D's also common but in this scenario, cert problems will cause exactly this issue. Pretty sure B is right-correct me if I’m missing something.
A is wrong, D. Saw similar on a practice test, duplicate messages usually mean the endpoint isn't acking fast enough.
D
B . Pub/Sub push retries happen if the SSL handshake fails, which is what you'd get with an out-of-date cert, so that can totally create dupes. D is a common cause too but the HTTPS angle makes B more likely here. Agree?
Pretty sure it's B. Pub/Sub push won't deliver properly if the SSL cert is expired so you get duplicate messages.
Its B here. If the SSL cert is expired or invalid, Pub/Sub can't complete the push and message delivery keeps retrying, causing duplicates. D usually fits but this one calls out HTTPS issues specifically. Anyone disagree?
Nah, I don’t think it’s D here. B is the catch-Pub/Sub push fails when certs are invalid, so messages aren’t acknowledged and you get retries (hence duplicates). D is a standard culprit but this question points at HTTPS/SSL issues.
Hard to say, B. If the SSL certificate is out-of-date, Pub/Sub can't complete the HTTPS handshake, so it keeps retrying and you get duplicate messages. D makes sense for missed acks, but here the cert problem explains the HTTPS retries. Pretty sure that's right.
Had something like this in a mock, picked D. Not acknowledging messages fast enough makes Pub/Sub resend them, so you get duplicates. I think that's a more common cause than SSL issues, but open to other takes.
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